Sun-tracking daylighting apparatus

ABSTRACT

A solar lighting apparatus of the sun tracking type for guiding sunlight into a building by using light reflecting means ( 30 ), the apparatus comprising the light reflecting means ( 30 ) for reflecting sunlight, drive means ( 60 ) for driving the light reflecting means, control means ( 70 ) for controlling the drive means to orient the light reflecting means toward the direction of the sun, and power source means ( 20 ) for supplying electric power to the drive means and the control means. The power source means ( 20 ) comprises a main power source unit ( 22 ) chargeable by a solar cell panel ( 40 ) for supplying electric power to the drive means ( 60 ) and the control means ( 70 ), and a backup secondary cell ( 24 ) chargeable with the electric power from the main power source unit for supplying electric power to the control means ( 70 ). The control means ( 70 ) comprises real time clock means ( 75 ) for measuring time, and a CPU ( 76 ) for calculating the direction of the sun based on data as to time measured by the clock means and controlling the operation of the drive means. The CPU ( 76 ) is switchable from a sleep mode to an active mode in operating state based on the time data from the clock means ( 75 ).

FIELD OF THE INVENTION

[0001] The present invention relates to solar lighting apparatus of thesun tracking type, and more particularly to a solar lighting apparatusof the type mentioned which has a power source chargeable by a solarcell.

BACKGROUND ART

[0002] Solar lighting apparatus are adapted for use with a skylight borehaving an opening in the roof of a building and extending to the ceilingfor admitting sunlight into the interior of the building where sunlightis not available. The apparatus has light reflecting means, which isprovided at the upper end of the skylight bore for reflecting sunlightinto the interior through the bore.

[0003] Solar lighting apparatus of the sun tracking type are known whichcomprise light reflecting means directed toward the sun and maderotatable to track the sun so as to achieve an improved light admissionefficiency since the sun changes in position with time.

[0004] With the solar lighting apparatus of the sun tracking type, thelight reflecting means is rotated by a motor as a drive source. Themotor is so controlled that the reflecting means is thereby rotated totrack the sun during the daylight hours from sunrise till sunset and isfurther directed after sunset toward the position of sunrise on the nextday.

[0005] When used as a power source for the motor, the commercial powersource requires wiring from an interior receptacle, hence a need forlabor and time. Power sources of the solar cell type are thereforesuitable to use. With the power source of this type, a capacitor ischarged with electric power output from a solar cell and delivers anoutput voltage to a constant-voltage circuit, which supplies a constantvoltage to a motor drive source or the like.

[0006] When the power source of the solar cell type is used, it becomesimpossible to drive the motor if the power source is completelydischarged due to a spell of rainy or cloudy weather which results in aninsufficient amount of sunlight. If a capacitor of great output is usedto hold the system stabilized, the apparatus becomes costly.Accordingly, the power consumption required for the overall system needsto be as small as possible.

[0007] The means for controlling the driving of the apparatus inpreparation for an interruption of power supply from the power source isusually provided with a backup secondary cell. The control means hasincorporated therein data required for causing the light reflectingmeans to track the sun, and the data includes information, for example,as to the latitude and longitude of the site of installation of thesolar lighting apparatus. If such information is initialized,restoration of the system requires much labor. When a backup secondarycell of increased capacity is used to hold the system stabilized, theapparatus becomes more costly. For this reason, the secondary cell mustbe checked meticulously for the charged state.

[0008] An object of the present invention is to reduce the powerconsumption of the overall system of a solar lighting apparatus of thesun tracking type wherein a solar cell power source is used.

[0009] Another object of the invention is to ensure a specified amountof charge at all times by monitoring the charged state of a backupsecondary cell for control means for use in the solar lighting apparatusof the sun tracking type wherein a solar cell power source is used.

DISCLOSURE OF THE INVENTION

[0010] To overcome the problems described above, the present inventionprovides a solar lighting apparatus of the sun tracking type for guidingsunlight into a building by using light reflecting means, the apparatuscomprising the light reflecting means for reflecting sunlight, drivemeans for driving the light reflecting means, control means forcontrolling the drive means to orient the light reflecting means towardthe direction of the sun, and power source means for supplying electricpower to the drive means and the control means, the power source meanscomprising a main power source unit chargeable by a solar cell panel forsupplying electric power to the drive means and the control means, and abackup secondary cell chargeable with the electric power from the mainpower source unit for supplying electric power to the control means, thecontrol means comprising real time clock means for measuring time, and aCPU for calculating the direction of the sun based on data as to timemeasured by the clock means and controlling the operation of the drivemeans, and the CPU being switchable from a sleep mode to an active modein operating state based on the time data from the clock means.

[0011] The CPU controls the operation of the drive means in accordancewith the time data from the clock means when in the active mode and isthereafter switched to the sleep mode. Stated specifically, the mainpower source unit is electrically connected to the control means and thedrive means by way of a main power source switch, and the CPU turns onthe main power source switch to drive the drive means and move the lightreflecting means upon finding that the present time is in a time zonefor tracking the sun when in the active mode and is thereafter switchedfrom the active mode to the sleep mode in operating state, or isswitched from the active mode to the sleep mode in operating statewithout driving the drive means when finding that the present time isnot in the time zone for tracking the sun.

[0012] The CPU checks the backup secondary cell for the amount of chargetherein in the active mode, and can thereafter be switched to the sleepmode. Stated more specifically, a charging switch is provided betweenthe main power source switch and the backup secondary cell, and the CPUchecks the secondary cell for the amount of charge therein in the activemode, turns on the charging switch when detecting a value lower than apredetermined amount of charge and is thereafter switched to the sleepmode.

[0013] The secondary cell can be charged in preference to the operationof the drive means.

[0014] A memory for storing data as to the latitude and longitude of thelocation of installation of the solar lighting apparatus can be includedin the real time clock means. In this case, the backup secondary cellmay back up the real time clock means only.

[0015] With the solar lighting apparatus of the sun tracking type of theinvention, the CPU is set in the sleep mode and is changed over to theactive mode only when interrupted by the real time clock means in aspecified cycle. In the active mode, the CPU is returned to the sleepmode when not in the sun tracking time zone, or the CPU controls theoperation of the drive means as specified, checks the backup secondarycell for the amount of charge therein when in the sun tracking timezone, and is thereafter set in the sleep mode again. Thus, the controlmeans and the drive means remain out of operation until the CPU issubsequently interrupted by the real time clock means. This reduces thepower consumption of the overall system of the apparatus to a minimumessential level.

[0016] When an interrupt is made by the clock means in the specifiedcycle, the backup secondary cell is checked for the amount of chargetherein and charged if the detected value is less than a predeterminedlevel. Thus, the predetermined amount of charge can be retained in thecell at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a block diagram showing an electric system of a solarlighting apparatus of the sun tracking type of the invention.

[0018]FIG. 2 is a flow chart showing an exemplary control operation tobe performed by control means of the solar lighting apparatus of theinvention.

[0019]FIG. 3 is a flow chart showing another exemplary control operationto be performed by the control means of the solar lighting apparatus ofthe invention.

[0020]FIG. 4 is a perspective view of an embodiment of solar lightingapparatus of the sun tracking type.

[0021]FIG. 5 is a view in section taken along the line V-V in FIG. 4.

[0022]FIG. 6 is a plan view of the embodiment of solar lightingapparatus of the sun tracking type.

[0023]FIG. 7 is a perspective view of a portion including a supportframe through a control box.

[0024]FIG. 8 is a view in section of the control box as attached to adome.

BEST MODE OF CARRYING OUT THE INVENTION

[0025] The preferred embodiment of the invention will be described belowin detail with reference to the drawings.

[0026] FIGS. 4 to 8 show the construction of embodiment of solarlighting apparatus of the sun tracking type wherein a solar cell powersource is used.

[0027] Although the illustrated solar lighting apparatus has lightreflecting means as supported in suspension, the light reflecting meansis not limited to the suspended type, but the invention is of courseapplicable to solar lighting apparatus having light reflecting meanswhich is installed as supported at its lower portion.

[0028] For convenience of explanation, the direction toward the sun Swill be referred to as “front,” and the opposite side as “rear” as shownin FIGS. 5 and 6.

[0029] The solar lighting apparatus 10 of the sun tracking type isinstalled at the upper end of a skylight bore 90 extending from the roofof a building through the ceiling thereof as seen in FIG. 5.

[0030] The skylight bore 90 has at its upper end an opening formed in aroof portion of the building. The bore 90 is generally in the form of asquare measuring about 120 cm in the length of one side, and is orientedin a direction which changes with the size, structure of the building orroom, direction the building or room faces, required amount of light andlike conditions.

[0031] An inner wall 92 defining the skylight bore 90 has a mirrorsurface so as to guide the rays of light L reflected by the apparatus 10efficiently into an interior space. Provided at the lower end (at theinterior ceiling side) of the bore 10 is a transparent interiordiffusion plate (not shown) for diffusing the light admitted into theinterior space.

[0032] With reference to FIGS. 4 to 6, the sun tracking solar lightingapparatus 10 comprises a dome 15 mounted over the upper end of theskylight bore 90, light reflecting means 30 disposed within the dome andsupported in suspension by the dome, and a control box 50 for rotatingthe reflecting means 30 to cause the means to track the sun.

[0033] The dome 15 is a transparent or translucent cover for protectingthe light reflecting means 30 from wind, rain, dust, etc. and preventingthese from ingressing into the interior. The illustrated dome 15 isprepared from acrylic resin and has a generally semispherical centralportion and a peripheral edge portion which is square in conformity withthe shape of the skylight bore 90. The dome 15 is not limited to thesemispherical shape but can be in any of various shapes such as squareor rectangular shape and conical or pyramidal shape.

[0034] Formed in the top of the dome 15 centrally thereof is a mounthole (12) for attaching the control box 50 to the dome. The dome hasscrew bores equidistantly spaced apart around the mount hole for use infastening the control box 50 with screws.

[0035] The light reflecting means 30 comprises a plurality of reflectivepanels 31, 32, 33 attached to a support frame 34 and is disposed insidethe dome 15 and supported thereby in suspension.

[0036] The support frame 34 is in the form of a bar inclined downwardtoward the front (toward the sun S) and has a suspending hook 35projecting upward from a portion thereof slightly rearward from itsmidportion (see FIG. 7). The support frame 34 is provided with the threereflective panels 31, 32, 33.

[0037] Each of the reflective panels 31, 32, 33 is a mirror forreflecting sunlight and is prepared, for example, by affixing to alightweight styrene resin plate a resin film having a mirror surfaceformed by vacuum evaporation of aluminum. The reflective panels 31, 32,33 are arranged as supported by the front end, middle portion and rearend of the support frame 34, with their panel surfaces opposed to oneother.

[0038] In order to achieve a high efficiency of light admitting evenwhen the sun is at a low altitude, it is desired that the reflectivepanels 31, 32, 33 be made indifferent sizes and attached at differentangles.

[0039] Stated more specifically, the front reflective panel 31 ispreferably smaller than the other panels in both height and width, whilethe middle reflective panel 32 is preferably greater than the rear panel33 in width although smaller than this panel 33 in height. Furtherpreferably, the reflective panels 31, 32, 33 as arranged from the rearforward have their lower ends positioned at progressively higher levels.

[0040] The panels 31, 32, 33 have respective angles of inclination θ1,θ2 and θ3 which decrease from panel to panel toward the front. Thus itis desired that the panels be attached so as to incline forward(θ1<θ2<θ3). For example, these angles θ1, θ2, θ3 as shown in this orderfrom the front rearward can be 55°, 65°, 70°, respectively. Thisachieves an optimum light admitting efficiency in accordance with thealtitude of the sun.

[0041] With reference to FIGS. 7 and 8, a solar cell support frame 42extends forward from a hook 35 of the support frame 34, and the solarcell panel 40 facing obliquely upward is attached to the front end ofthe frame 42.

[0042] The solar cell panel 40 is attached to the support frame 42 ofthe light reflecting means 30 so as to be rotatable with the frame 34and is therefore adapted to track the sun with the reflecting means 30and to generate electricity with a high efficiency during the daylighthours.

[0043] The solar cell panel 40 has connected thereto wiring 46 and iselectrically connected to power source means 20 by the wiring 46.

[0044] The control box 50 is fitted in the mount hole 12 in the top ofthe dome 20, supporting the support frame 34 of the light reflectingmeans 30 in suspension.

[0045] The control box 50 has a casing 52 having housed therein drivemeans 60, control means 70, the power source means 20, etc.

[0046] The casing comprises a casing body 52 in the form of a cylinderhaving a bottom, and a closure 56 as seen in FIG. 8. The closure 56 hasan outer edge extending outward as if covering a flange 54 of the casingbody 52, closing an upper opening of the casing body 52.

[0047] A gear box 64 providing the drive means 60 is disposed inside thecasing body 52.

[0048] A motor 62 is coupled to the rotating shaft 66 by a reductiongear mechanism (not shown) in the gear box 64.

[0049] The control means 70 comprises various electronic componentsmounted on a circuit board 74 and required for controlling the drivemeans 60, etc. Angle detecting means 72 is provided on the lower surfaceof the circuit board 74 centrally thereof.

[0050] The angle detecting means 72 serves to detect the angle of thelight reflecting means 30 and is connected to the rotating shaft 66 by acoupling. Usable as the angle detecting means 72 is a potentiometer havea resistance value variable with the value of the angle of rotation.

[0051] The board 74 is provided with the power source means 20, whichcomprises a main power source unit 22 and a secondary cell 24. Usable asthe main power source unit 22 is a capacitor of great capacity(supercapacitor). Usable as the secondary cell 24 is a manganesedioxide-lithium secondary cell.

[0052] Next, a description will be given of the electric system of thesolar lighting apparatus of the invention with reference to the blockdiagram of FIG. 1.

[0053] The electric power generated by the solar cell panel 40 duringdaylight hours is supplied to the main power source unit 22 and storesin the capacitor of the unit. Generally the unit 22 includes a constantvoltage circuit for supplying a constant voltage to the load, inaddition to the capacitor.

[0054] The main power source unit 22 is electrically connected via amain power source switch 26 to the drive means 60 for rotating the lightreflecting means 30 and to the control means 70 for controlling thedrive means, etc. and supplies power to the drive means 60 and thecontrol means 70.

[0055] The present apparatus has another power source means, i.e., abackup secondary cell 24 for supplying power to the control means 70. Acharging switch 28 is provided between the main power switch 26 and thecell 24,

[0056] The drive means 60 is connected to the angle detecting means 72and the light reflecting means 30.

[0057] The control means 70 has a real time clock IC 75 serving as realtime clock means, CPU 76, motor drive circuit 77 and angle detectorcircuit 78.

[0058] The real time clock IC 75 prepares time data and interrupts theCPU in a specified cycle. A memory having stored therein data as to thelatitude and longitude of the location of installation of the solarlighting apparatus can be included in the clock IC.

[0059] The CPU 76 receives the time data from the real time clock IC 75,calculates the direction of the sun based on the data as to the timemeasured by the IC 75 and controls the operation of the drive means 60.The CPU further checks the backup secondary cell for the amount ofcharge therein and monitors the system to check abnormalities or thelike.

[0060] The motor drive circuit 77 is connected to the CPU 76 and drivesthe motor 62 under the control of the CPU 76 to cause the lightreflecting means 30 to move for tracking the sun.

[0061] The angle detector circuit 78 is connected to the CPU 76. Theresult of detection by the angle detecting means 72 is sent to the CPU76.

[0062] Next, the flow of control by the control means of the solarlighting apparatus of the invention will be described next withreference to the flow chart.

[0063] Referring to FIG. 2, when use of the solar lighting apparatus isstarted in step 100, the CPU is set in a sleep mode (step 102). The term“sleep mode” refers to a mode wherein the CPU and the peripheral devicesthereof are held out of operation and which includes a state involvingno consumption of electric power.

[0064] The real time clock make an interrupt to the CPU in a specifiedcycle (step 104). This cycle is the interval at which the solar cellpanel and the light reflecting means track the sun, and the shorter theinterval, the higher the efficiencies of power generation and lightadmission are, but the greater the power consumption is. For the solarlighting apparatus of the present invention to achieve the desired powergeneration and light admission efficiencies, with the increase of powerconsumption suppressed, the cycle of interrupting the CPU by the realtime clock is set at 10 minutes. However, this cycle can of course beset suitably at an optimum period of time in accordance with thelatitude and longitude of the location where the solar lightingapparatus is installed.

[0065] When the CPU is found interrupted by the real time clock in step106, the CPU is set in an active mode. The term “active mode” means amode wherein the CPU executes a program.

[0066] In this active mode, the CPU obtains data as to the present timefrom the real time clock (step 110).

[0067] Next, an inquiry is made as to whether the present time is in atime zone for tracking the sun (step 112). The term “sun tracking timezone” means daylight hours from sunrise to sunset, during which thelight reflecting means is moved to track the sun and guide sunlight intothe interior. When the inquiry is answered in the negative, step 102follows again to set the CPU in the sleep mode and avoid uselessconsumption of power.

[0068] When the present time is in the sun tracking time zone, thesequence proceeds to step 114, wherein the main power source switch isturned on. An inquiry is then made as to whether the current movement isthe last movement in the sun tracking time zone (step 116).

[0069] If the inquiry of step 116 is answered in the negative, step 120follows, in which the CPU calculates an angle of movement of the lightreflecting means. The drive means rotatingly moves the reflecting meansonly by the angle indicated by the CPU to position the light reflectingmeans anew (step 122). At this time, the solar cell panel is rotatinglymoved at the same time.

[0070] When the inquiry of step 116 is answered in the affirmative, areverse rotation mode is set for the light reflecting means (step 118).When this mode is set, the angle of movement of the light reflectingmeans is set to the position of sunrise in the following morning in thenext step 120. The light reflecting means is reversely rotated andpositioned anew (step 122).

[0071] The amount of charge in the backup secondary cell is checked instep 124. The voltage is checked as a typical indicator. Next, aninquiry is made as to whether the cell voltage is lower than apredetermined voltage (step 126). The predetermined voltage in thepresent embodiment is 2.7 V.

[0072] If the voltage of the secondary cell is lower than 2.7 V, thecharging switch is turned on (step 130) to charge the backup secondarycell with the power delivered from the main power source unit. When thenext step 132 finds that the charging switch is not off, the sequencereturns to step 102, with the main power source switch held on, to setthe CPU in the sleep mode.

[0073] When the voltage of the secondary cell is found to be at least2.7 V in step 126, the charging switch is turned off since there is noneed for charging (step 128). When the charging switch is found off instep 132, the main power source switch is turned off in the next step134, followed by step 102 again to set the CPU in the sleep mode.

[0074]FIG. 3 is a flow chart showing a procedure for checking thesecondary cell for the charge therein and charging the secondary cellwhich procedure is to be performed in preference to the operation of thedrive means.

[0075] Step 200 of starting the use of the solar lighting apparatusthrough step 214 of turning on the main power source switch are the sameas in FIG. 2 and will therefore not be described again.

[0076] When the main power source switch is turned on (step 214), thebackup second cell is checked for voltage (step 216). An inquiry is thenmade in step 218 as to whether the cell voltage is lower than 2.7 V(predetermined voltage). If the voltage is lower than 2.7 V, thecharging switch is turned on (step 222), charging the cell with thepower delivered from the main power source unit. If the charging switchis found not off in the next step 224, the sequence returns to step 202to set the CPU in the sleep mode.

[0077] When the voltage of the secondary cell is found to be at least2.7 V in step 218, the charging switch is turned off since there is noneed for charging (step 220). If the charging switch is found off instep 224, step 226 follows.

[0078] The backup secondary cell serves to back up the electric systemof the control means. The cell is checked for the charged state andcharged as required in preference to the operation of the drive means,whereby the control means is prevented from being initialized until themain power source unit is charged again even if the unit is completelydischarged temporarily.

[0079] In the case where a memory having stored therein data as to thelatitude and longitude of the location of installation of the solarlighting apparatus is incorporated in the real time clock IC, the backupsecondary cell can be so adapted as to back up the clock IC only of thecontrol means. The reason is that if the data as to the latitude andlongitude of the location of installation of the solar lightingapparatus is initialized, the restoration of the system requires muchlabor.

[0080] Step 226 of inquiring whether the current movement is the lastmovement in the sun tracking time zone through step 232 of positioningthe light reflecting means anew are the same as step 116 through step124 of FIG. 2. When the light reflecting means is positioned anew instep 232, the main power source switch is turned off in the next step234, followed by step 202 again to set the CPU in the sleep mode.

[0081] As described in detail with reference to the embodiment of solarlighting apparatus of the invention, the CPU is set in the sleep mode,and only when an interrupt is made by the real time clock in thespecified cycle, the CPU is switched to the active mode, in which theoperation of the drive means is controlled as specified in accordancewith the time data from the real time clock, the backup cell is checkedfor the charge therein and charging is effected as required, whereuponthe sleep mode is resumed. The control means and the drive meanstherefore remain out of operation until an interrupt is subsequentlymade by the real time clock. This results in minimized powerconsumption, stabilizing the system more effectively even if thecapacitor of the main power source unit has the same capacity as in theprior art.

[0082] The backup secondary cell is checked for the amount of chargetherein when an interrupt is made by the real time clock in thespecified cycle, charged if the charge is less than the predeterminedlevel and accordingly thus adapted to retain the predetermined amount ofcharge. The system is therefore exceedingly superior to the conventionalone with respect to stability even if the secondary cell has the samecapacity as conventionally.

[0083] In the case where the secondary cell is-used exclusively forbacking up the real time clock means, the cell can be further smaller incapacity.

INDUSTRIAL APPLICABILITY

[0084] The solar lighting apparatus of the sun tracking type is reducedin the power consumption of the overall system of the apparatus, permitsthe secondary cell for backing up the control means of the apparatus toretain the required amount of charge at all times, and is therefore veryuseful.

1. A solar lighting apparatus of the sun tracking type for guidingsunlight into a building by using light reflecting means, the apparatuscomprising the light reflecting means for reflecting sunlight, drivemeans for driving the light reflecting means, control means forcontrolling the drive means to orient the light reflecting means towardthe direction of the sun, and power source means for supplying electricpower to the drive means and the control means, the power source meanscomprising a main power source unit chargeable by a solar cell panel forsupplying electric power to the drive means and the control means, and abackup secondary cell chargeable with the electric power from the mainpower source unit for supplying electric power to the control means, thecontrol means comprising real time clock means for measuring time, and aCPU for calculating the direction of the sun based on data as to timemeasured by the clock means and controlling the operation of the drivemeans, and the CPU being switchable from a sleep mode to an active modein operating state based on the time data from the clock means.
 2. Thesolar lighting apparatus of the sun tracking type according to claim 1wherein the CPU controls the operation of the drive means in accordancewith the time data from the clock means when in the active mode and isthereafter switched to the sleep mode.
 3. The solar lighting apparatusof the sun tracking type according to claim 2 wherein the main powersource unit is electrically connected to the control means and the drivemeans by way of a main power source switch, and the CPU turns on themain power source switch to drive the drive means and move the lightreflecting means upon finding that the present time is in a time zonefor tracking the sun when in the active mode and is thereafter switchedfrom the active mode to the sleep mode in operating state, or isswitched from the active mode to the sleep mode in operating statewithout driving the drive means when finding that the present time isnot in the time zone for tracking the sun.
 4. The solar lightingapparatus of the sun tracking type according to claim 1 wherein acharging switch is provided between the main power source unit and thebackup secondary cell, and the CPU checks the secondary cell for theamount of charge therein in the active mode, turns on the chargingswitch when detecting a value lower than a predetermined amount ofcharge and is thereafter switched to the sleep mode.
 5. The solarlighting apparatus of the sun tracking type according to claim 1 or 2 or3 or 4 wherein the real time clock means includes a memory for storingdata as to the latitude and longitude of the location of installation ofthe solar lighting apparatus, and the backup secondary cell backs up theclock means only.